My invention relates to an integral combination of a hydraulic cylinder and a remotely activated valve. In particular, my invention is directed to a cylinder-valve assembly that is useful as part of an improved fork positioning system for front end loading refuse vehicles. My invention allows the forks on a front-end loader to be stowed in a safe position during over-the-road travel.
Hydraulic cylinders are used in numerous applications and find specific utility in the operation of heavy-duty commercial equipment and vehicles. In particular, refuse collection vehicles use a number of hydraulic cylinders to move the various mechanical parts of the vehicle. One particular type of refuse vehicle is the front-end loader which is used to pick-up and dump refuse or recycle bins and containers. Specific to front-end loaders is a pair of forks that are designed to engage a pair of lifting pockets normally located on the sides of a refuse container. These forks are pivotally connected to a pair of arms that raise the forks and the container up and over the top of the vehicle where the forks then rotate the container until its contents are dumped into a hopper located on top of the vehicle body. Once emptied, the procedure is reversed and the forks are rotated outwardly away from the vehicle and the arms are lowered to bring the container back to ground level. Both the forks and the arms are moved using hydraulic cylinders.
An important consideration in operating a front-end loader in over-the-road travel is to not exceed state and federal laws that regulate height limit for such vehicles. Currently, the law requires that no part of the vehicle exceed a height of 13xc2xd ft. When the vehicle is operated in over-the-road travel, the operator will usually raise the arms back to their maximum position and rotate the forks towards the vehicle as far as possible. A problem arises if the forks are not tucked far enough back to a position sufficient to avoid exceeding the maximum height limitation as required by law. Those skilled in the art have suggested several methods to avoid this problem. In some cases the operator will position the forks in a folded second position by manipulating a mechanical means, such as a pendulum that normally is set to prevent full rotation of the forks during a dump cycle. A second known method involves the use of a four-ported cylinder where two sets of hydraulic lines are routed from each of the two cylinders attached to the forks along the perimeter of the lift arms, eventually making their way back to the vehicle body where they are connected to two solenoid valves. This complicated system allowed the forks to be set in two double positions. A first double position when fully extended and a second double position that allowed the forks to be fully rotated to meet the height requirement. A major problem with this design was the need for an excessive amount of hydraulic lines and corresponding hydraulic connectors. The wear and tear on these hydraulic lines and connectors caused by the up and down motion of the arms resulted in frequent maintenance and downtime of the vehicle. Yet another fork folding system is disclosed in U.S. Pat. No. 5,984,609 where a cylinder speed control mechanism is used to slow the piston speed severely during the dump cycle to avoid over rotating the forks and losing the trash container into the hopper. Other systems were also tried that involved various combinations of hydraulic and mechanical stops and cams, each with inherent problems related to maintenance and reliability.
Until my invention, no one in the art had devised a unique combination of a remotely operated valve connected directly to a multi-port hydraulic cylinder. My invention provides a fork folding system that is reliable and requires little maintenance as compared to prior art systems.
Accordingly, a primary object of my invention is to provide a hydraulic cylinder-valve assembly for use on commercial vehicles, in particular refuse vehicle that eliminates multiple hydraulic lines and avoids costly maintenance and downtime.
Another object is to provide a fork folding system that allows front-end loading refuse vehicles to meet the 13xc2xd ft. height regulation for over-the-road travel.
Yet another object of my invention is to provide a fork folding system that can be activated by the vehicle operator without leaving the vehicle cab and by using a single control valve.
Other objects, features and advantages of the present invention will be apparent to those skilled in the art through familiarity with the discussion of the prior art, summary of the invention, detailed description, claims and drawings.
My invention overcomes the problems known to the art in operating hydraulic cylinders by providing an integral combination of a remotely operated valve and a double-acting hydraulic cylinder. The valve portion of the combination is connected directly to the cylinder body and is in direct fluid communication with two hydraulic fluid ports that partially control the extension and retraction of the cylinder plunger. By use of the term xe2x80x9cportxe2x80x9d I mean an opening in the cylinder where hydraulic fluid can flow into and out of the cylinder body. In addition to connecting directly with two ports on the cylinder, the valve is also connected via a single hydraulic line to a control value that in turn is connected to a control located in the vehicle cab that is manually operated by the vehicle operator. The control in the cab can be connected to the control value by a variety of means known to the air, including air, electrical or hydraulic. The internal workings of the valve are designed such that when it is in the closed position, one of the cylinder ports is sealed off from the other port and is capable of maintaining hydraulic pressure in a portion (or chamber) of the hydraulic cylinder. In this position, the valve prevents the cylinder plunger from fully retracting. When the valve is in the open position, both ports are in fluid communication with each other and the pressure can be relieved from the entire cylinder body allowing the plunger to fully retract.
The valve is opened and closed remotely, meaning that either an electrical signal or other means is used to activate the valve at a distance from the cylinder-valve assembly. Activation of the valve is typically from a normally open position to a closed position. In a preferred embodiment, the remotely activated valve is a solenoid valve that is activated by some remote means, preferably by a switch that is opened or closed either manually or automatically. In certain circumstances the switch can be opened or closed as a result of some predetermined condition occurring. When the hydraulic cylinder-valve assembly is used on a front end loading refuse vehicle the remotely activated valve can be activated by the vehicle operator from within the cab of the vehicle via a switch or through some other remote device that causes the valve to open or close. In effect, the valve allows the cylinder to retract to two positionsxe2x80x94a dump position and a tucked position.
The dump position is the partially retracted position that prevents accidental loss of the refuse container into the vehicle hopper and greatly reduces the possibility of damage to the packer. The tucked position is when the cylinder is fully retracted and the attached forks are rotated back towards the top of the vehicle to avoid violating height regulations during over-the-road travel. In a particular preferred embodiment of my invention, a limit switch that is designed to sense a predetermined position of the arms during elevation over the vehicle remotely activates each of the valves connected to the cylinders causing them to close and thus prevent complete retraction of the cylinder plunger and complete rotation of the forks. The use of a limit switch provides a type of fail-safe mechanism that prevents the vehicle operator from accidentally rotating the forks to the tucked position during the dump cycle.